Whether on the ground or in flight, an aircraft communicates using a radio link with external nodes, for example with an air traffic control (ATC) center, station, or facility, as well as to any communications center for communications with the airline, in order to exchange data relating especially to the movement of the aircraft. In particular, when an aircraft is in flight, the crew on board the aircraft, for e.g., the pilot or the co-pilot, communicates by radio link with the ground staff, for e.g., the air traffic controller, in order to exchange flight related data.
For example, the communications between the ATC center and the aircraft may comprise data relating to a flight sector, a flight level, a speed of the aircraft, a frequency of transmission and/or reception of messages to be exchanged with ground staff, etc. In addition, the ATC center and aircraft communications may relate to very high frequency (VHF) communications.
Indeed, each area of aeronautical space, such as airports and airspace, is sectorized, i.e., broken into virtually defined airspace regions that are managed by a designated communications center. For example, each sector of airspace is known as an ‘ATC sector’, which is managed by one designated ATC center. There may be one or several active ATC sectors in a given flight information region (FIR). In some aspects, a number of active ATC sectors is dynamically managed by the designated ATC center depending on a density and/or complexity of air traffic. Each active ATC sector is assigned a single VHF frequency. In a given ATC sector, therefore, an aircraft will only interact with the designated ATC center on the assigned VHF frequency channel.
When an aircraft passes through one ATC sector and enters a new ATC sector, the crew of the aircraft needs to know the frequency of the radio channel of the ATC center of the new ATC sector. Thus, the crew of the aircraft needs to be informed of the radiofrequency of the ATC center of the new ATC sector before leaving the former ATC sector so that it can come into contact with the ATC center of the new ATC sector as soon as it enters the new ATC sector. For example, when an aircraft reaches an end of a first ATC sector, an ATC center associated with the first ATC sector may transmit the new VHF frequency on which the pilot will be communicating with the ATC center of the second ATC sector to a crew member (e.g., pilot) in charge of communications on board the aircraft. Generally, the pilot then tunes to this new frequency on a display unit of the cockpit, e.g., a radio and audio management panel (RMP).
Generally, through regulations-specified documents such as maps, the pilot is aware of which ATC centers the pilot will be communicating with throughout the flight, depending on the maneuvers that he will have to make (for example landing, take-off, cruising, etc.). Thus, when the pilot receives information on the frequency of the new ATC sector, for the most part, the pilot is already aware of the ATC sector concerned. Regardless, the frequency of the new ATC center is communicated to the pilot by the previous ATC center so that the pilot can prepare to use the new frequency by tuning the channel frequency on a display unit of the cockpit. However, this procedure can be problematic without any corroborating information. For example, amplitude modulation (AM), which is predominately used in aircraft radio communications, can provide high noise level and signal attenuation, thereby decreasing audio quality of the transmission. Such a decrease may result in a mistake in channel tuning by the pilot.
To resolve this issue, interactive display screens that present communication frequency values for ATC centers within an aircraft's radio frequency horizon and provide useful information regarding each frequency are used to enable the pilot to confirm that the pilot is tuning to the correct frequency. Databases which, for example, associate the assigned frequency to the respective ground station, in addition to the type of services provided, designated operational coverage (DOC), and boundaries of the FIRs, may provide such useful information.
Yet, such displays tend to present all possible communication frequency values for ATC centers within the aircraft's radio frequency horizon (regardless of flight level, services provided, occupation rate of frequency channel, etc.), which, while useful, can be unwieldy for a pilot trying to corroborate the new communication frequency provided by an ATC center. Specifically, these displays include communication frequency values for channels with a high occupancy rate mixed in with channels having a low occupancy rate. However, frequency channels that are highly trafficked (i.e., have a high occupancy rate) generally have a higher probability of being selected by the previous ATC station as the new VHF frequency on which the pilot will be communicating with the new ATC station than lower frequency channels.
Accordingly, there is a need for an ability to organize these displayed frequency channels in order to sort high occupancy channels as higher priority channels and low occupancy channels as lower priority channels, thereby simplifying evaluation of which frequencies may be communicated by a previous ATC center to the pilot.